According to the WSJ, some Internet service providers, aiming to get into the growing online ad business, are using new gear to observe and analyze all of their customers’ online activities.

CenuryTel’s system allows it to observe and analyze the online activities of its Internet customers, keeping tabs on every Web site they visit.

The equipment is made by a Silicon Valley start-up called NebuAd Inc. and installed right into the phone company’s network.

NebuAd takes the information it collects and offers advertisers the chance to place online ads targeted to individual consumers. NebuAd and CenturyTel get paid whenever a consumer clicks on an ad.

This technique — called behavioral targeting — is far more customized than the current method of selling ads online.